Method and apparatus for straightening well bore holes



April 8, 1958 S. R. KNAPP METHOD AND APPARATUS FOR STRAIGHTENING WELL BORE HOLES Filed Feb. 1. 1955 2 Sheets-Sheet 1 F G FIG 3 r 11 F IG-2 f INVENTOR. 7 SETH R. KNAPP ATTORNEYS April 8, 1958 s. R. KNAPP METHOD AND APPARATUS FOR STRAIGHTENING WELL BORE HOLES Filed Feb. 1. 1955 2 She ets-S heet 2 FIG -4 FIG-6 IN V EN TOR.

SETH'R. KNAPP ATTORNEYS METHOD AND APPARATUS FOR STRAIGHTEN- ING WELL BORE HOLES Seth R. Knapp, Lindsay, Okla. Application February 1, 1955, Serial No. 485,418

(Ilaiins. (Cl. 2551.6)

This invention relates to a method and apparatus for straightening well bore holes.

In drilling well bores in the earth, there is sometimes a tendency for drilling bits to drift from the vertical. For example, such deviation may be due to the fact that the formations being drilled do not line in a horizontal plane but are tilted therefrom. As the drill bit cuts through such a tilted hard formation, it may be crowded away from the vertical until the drill collar rests against a wall of'the' bore hole and stops any further such deviation. It will be apparent that if several such hard formations are encountered, the resulting cumulative deviation may become substantial, and the present invention is directed to a method and apparatus for bringing such deviated bore holes back to true vertical.

It has been found that deviation can be minimized by keeping light weight on the bit, but this tends to result in a slow rate'of penetration which is undesirable from a cost standpoint. Use of oversized drill collars or reamers often causes crowding or jamming of the drill string. Furthermore, weight applied on the drill collars may cause them to buckle and so turn the hole from vertical, since the cutting face of the bit is tilted slightly from right angles to the vertical axis of the hole as the drill string bends. As the bit tends to go in the direction it is facing, the bent drill string causes the bit to drill further away from vertical. If, however, the cutting face of the bit could be tilted a predetermined amount in the proper direction assoou as the bore hole leaves the vertical, the hole could be prevented from deviating to an undesirable extent;

It isa primary object of this invention to provide a method and apparatus for straightening well here holes which will utilize the plumb'bob effect of thedrill string to guide the cutter or bit on a line parallel to but slightly offset from the vertical portion of the original bore.

An additional object of this invention is to provide apparatusfor straightening well bores which is of simple construction and mode of operation and which will cut a vertical bore parallel to but slightly offset from the vertical portion of the original bore.

t Another object of the present invention is to provide apparatus whereby well bore holes which have deviated from vertical may be straightened at a point where deviation has become excessive. 7

It is also an object of the present invention to provide a method whereby well bore holes which have deviated from vertical may be straightened or returned to true vertical at a point near the original point of deviation without the necessity of lowering the cutter or hit and drill pipe to the bottom of the deviated bore hole.

Other objects and advantages of the invention will be apparent from the following description, the accompanying drawing and the appended claims.

In the drawing- Fig. 1 illustrates apparatusin accordance with the invention for .straightening bore holes;

nited States Patent 0 ence'nurneral 10 indicates a drill pipe collar about which is carried a centering guide or stabilizer 11 for centering 2,829,864 liatented Apr. 8, 1958 Fig. 4 is an illustration of a modification of the invention wherein a deviated bore hole is straightened near the original point of deviation;

Fig. 5 is a view of a modification of apparatus provided by the invention; and

Fig. 6 is another view of modified straightening apparatus provided tion.

Referring to the drawing, which illustrates preferred embodiments of the present invention, in Fig. 1 referin accordance with the present inven;

the collar within the well bore. The lower end of collar 10 is attached to the lower end of a rotary drill stringh Connected at one end to the drill pipe collar 10 is a hero ible upper joint 12, and conected to the other end of the: joint 12 is a link 13 which is substantially rigid or resist; ant to bending as will be apparent from an inspection of,

Attached to the lower or other end of joint 14 is a lower drill collar .16 having a bit 18 connected to its lower end. A lower centering guide or stabilizer 17 is.

located about collar 16. The location of the centering guide 17 maylikewise be varied with respect to the bit 18 to compensatefor particular conditions encountered when straightening a particular deviated bore hole. Each centering guide or stabilizer 15 and 17 is mounted so that its longitudinal ribs are either in contact with or in closely spaced relation to the walls of the bore, preferably having an outer diameter slightly less than the dimeter of the bore,-and thus the centering guides are fixed against any substantial lateral motion within the bore and are maintained relatively stationary in the hole, while the collar 16 and link 13rotate within their respective stabilizers.

Joints 12 and 1 4 may be provided by any suitable type of flexible members.

For example, Fig. 2 illustrates a type of articulated flexible joint with which satisfactory results are obtained. The joint comprises a hollow socket mmeber 25, a skirt member 26 threadedly engaged at 27 to the socket member, and a ball member 30 positioned within the skirt member 26 and resting in sliding engagement upon curved inner surface 31 of skirt member 26. A series of pins 32 extend through'the wall of skirt member 26 and have located on each of their inner ends a roller 33. Cut-away portions 35 are provided in as shown at 45. Complementary cams are provided at 46 on the inside of the skirt portion and at 47 on the shaft 36 to limit the deviation from axial alignment of the shaft 36 and the socket member 25.

Through the center of socket member 25, ball member a t t a 3 30 and shaft 36 are provided passages 50 and 51, respectively, which are axially aligned for purposes of conducting drilling fluid through the joint in the usual manner. Seals are'provided at 53 between the ball member 30 and the socket member 25 and at 54 between the ball member 30 and the skirt member 26, to prevent the drilling fluid from escaping from passages 50 and 51, and also to prevent access of drilling mud into these passages. In some instances it may be desirable to place a sleeve 55 about the flexible joints to prevent the joint from digging into the side of the bore hole or traveling around the inside of the hole when the drill is rotated. Such sleeves will allow the joints 12 and 14 to rotate and bend freely, but keep them from direct contact with the sides of the bore hole. However, for purposes of clarity and simplicity the sleeves have been omitted from joints 12 and 14 in Fig. 1.

In Fig. 4 another type of flexible joint is illustrated at 12' and 14' as including a relatively thin section of drill pipe which will flex under forces which would not affect the rest of the drill collar.

In carrying out the method of the invention, the part 13 forms a floating link attached between the drill collar at the end of the drill pipe string and the lower drill collar 16. A stabilizer having an outer diameter just slightly smaller than the bore hole is attached about the floating link either at its center or at a predetermined distance from the center, depending upon the amount of throw desired. The link can rotate freely within the centering guide, such a feature being desirable to avoid the guide digging into the wall when the link rotates during a drilling operation. With these parts assembled as shown, the stabilizer forms a pivot providing for tilting of the link within the bore hole.

'When the parts are assembled as just described, the drill string is lowered in the bore hole until the floating link 13 is within the deviated portion of the bore hole, and the stabilizer 15 attached about floating link 13 is resting on the lower wall 64. At this point bit 18 is usually touching the bottom of the deviated hole.

Referring to Fig. 3, the members 1018 are shown schematically first in a dotted position illustrative of the relation of these members as they are lowered into the deviated bore hole, and then in full lines showing the tilting action of link 13 about stabilizer 15 as the drill collar 10 passes from the vertical bore portion 60 into the deviated portion 61. Due to the horizontal force, indicated by arrow 63, resulting from the plumb bob action of drill string 10 at joint 12, this joint contacts the lower wall 64 of deviated portion 61, and consequent pivoting of link 13 about stabilizer 15 causes joint 14 to be urged in the opposite direction against the upper wall 65 of deviated bore portion 61.

The magnitude of the horizontal force indicated at 63 will be seen to be considerable, when it is realized that the weight of the drill string may be as great as 90 pounds per foot, and that the action of gravitational forces on drill string 10 tending to maintain the string along a true vertical line will result in a substantial horizontal component (force 63) which breaks or flexes the flexible joint 12, thus permitting the socket member of the joint to contact lower wall 64. When the joint is so flexed, with the resultant pivoting of link 13 as above described, the lower joint 14 will also be flexed in an opposite direction, since it will be moved from the center line of the bore through an amount proportional to movement of joint 12 from that center line. For example, if stabilizer 15 is placed at the exact center of link 13 the movements of joints 12 and 14 will be equal although opposite.

This movement of joint 14 causes the lower drill collar 16 to pivot about lower stabilizer 17, with consequent urging of the cutting face of bit 18 away from a position perpendicular to the center line of the deviated bore the dotted continuation 67 of the hole in Fig. l.

portion and toward a position wherein it would eventually be perpendicular to the center line of the vertical bore portion 60. Since stabilizer 17 is placed adjacent bit 18, for any given movement of joint 14 and the upper end of drill collar 16 the movement of bit 18 will be considerably smaller, but on the other hand,'the force multiplication will be considerable.

Rotary motion of the drill is then initiated, and the bit 18 will be directed along a line which gradually curves until it is substantially parallel to, but horizontally offset from, the original vertical axis of the hole as showxfby ter suitable tests have been made to determine that the bore hole is again directed along a truly vertical line, the apparatus may be withdrawn and removed from drill collar 10, and normal drilling resumed with a bit at the end of that collar.

When drilling through relatively soft formations, if the bore hole drifts away from true vertical it is possible to straighten it with the apparatus provided by this invention without dropping the bit to the bottom of the bore hole. Fig. 4 illustrates the apparatus modified to perform such straightening operation. It will be noted that flexible joint 12'. is just within the deviated portion 61, and that centering guide 17 has been moved on collar 16 to a point approximately midway between bit 18 and joint 14' in order to provide a pivot for collar 16.

With the apparatus so supported, the weight of drill collar '10 causes it to hang vertically, thus urging joint 12' against lower wall 64 and causing link 13 to tilt about its centering guide 15. This tilting of the floating link causes joint 14' to move in the opposite direction, toward upper wall 65, and this movement in turn tilts lower drill collar 16 about its centering guide 17, and urges the edge of bit 18 into lower wall 64. The drill string is then rotated, and the bit 18 will cut into lower wall 64 toward a direction parallel to the original vertical bore hole 60. Once enough of this cutting has been completed to form a ledge or platform, by boring away a portion 63'as shown in Fig. 4, the force supporting the drill string can be at least partially removed, and weight applied to the bit 18 to increase the cutting rate as desired.

Fig. 5 shows a modified form of apparatus which may also be used in accordance with this invention for straightening deviated bore holes. This apparatus includes a. long unitary drill collar 70 which has a diameter substantially smaller than the diameter of the bore hole. At the lower end of collar 70 there is fixed a bit 71, and a stabilizer or centering guide 72 having an outer diameter just slightly smaller than the diameter of the bore hole is placed about the drill collar spaced a substantial distance above bit 71. Bearing in mind that a deviation from vertical of approximately 6 or more is generally considered undesirable, it must be remembered that for purposes of illustration, the angles of deviation of the bore hole, and the angles of flexure of the flexible joint and flexible members, must necessarily be exaggerated in the drawings.

In using the apparatus of Fig. 5 the stabilizer 72 placed about drill collar 70 will have a stiffening effect upon the drill collar for at least a few feet on each side of the drill collar, and therefore the portions of collar 70 adjacent stabilizer 72 will be less subject to bending than portions of the collar farther away from the stabilizer. The apparatus of Fig. 5 is attached to the bottom of an ordinary heavier drill collar 10 and lowered into the deviated bore. When stabilizer 72 enters the deviated bore portion 61, the plumb bob efl'ect of the heavier drill collar 10 will cause the adjacent attached portion 73 of the collar 70 to flex and contact lower wall 64.

Stabilizer 72, having a diameter only slightly smaller than the bore, cannot tilt appreciably within the bore, and due to the stiffening effect of the stabilizer upon collar 70 a portion 74 of the collar 70 somewhat below stabilizer 72 will be flexed in an opposite direction so as to contact upper wall 65 of the deviated bore portion. Since bit 71 fits relatively snugly within the bore, it cannot move laterally to any appreciable extent, and so the flexure of collar 70 and 74 will tilt bit 71 toward a position wherein its cutting face is approaching a line perpendicular to the vertical bore portion.

Whether using the apparatus of Fig. 1, Fig. 4, or Fig. 5, once the new hole 67 has been cut to a depth equal to the distance between joint 14 and bit 18, a test should be run to determine if the new hole 67 is still slightly inclined from true vertical and if so how much. If the hole is substantially straightened, that is, returned to within permissible limits of deviation from true vertical, then the bit 18 may be attached directly to the end of the dril collar and drilling resumed in the normal manner. Alternatively, it is possible to continue drilling with apparatus such as shown in Fig. 1. When used for such continued drilling, this apparatus will afford a constant correction and if bit i8 is crowded to one side in spite of the action of centering guide 17, the apparatus will automatically act to direct the bit back toward true vertical.

In the event that the bore hole has not been straightened enough during the course of the above mentioned opera tion, it then becomes desirable to make certain that the upper flexible joint 12 is not forced against the upper wall 65 at the intersection of the deviated portion 61 with the newly bored portion 67, as this would reverse the action of floating link 13. Provision of the stabilizer 11 about the collar 10 at a distance of about twenty to thirty feet will hold that joint 12 in contact with lower wall 64 while further straightening is accomplished.

Fig. 6 illustrates an alternative method of continuing the straightening of the bore hole wherein the link 13 has been removed, a stabilizer 82 is attached around drill collar 10 about five to ten feet above the bottom of the rotary drill string, and a drill collar 84 having a bit 35 at its bottom end, and a centering guide 86 immediately above the bit, is attached to joint 12. This apparatus will force joint 12 to rest against upper wall 65 as it progresses into the newly drilled portion 67 of the bore hole, and bit 85 will continue to drill the hole in a direction away from the original deviated portion 61 and toward true vertical until a survey indicates that the hole is straightened to within acceptable limits. At that time the apparatus may again be withdrawn from the bore hole, the drill collar 84 removed, and bit 18 attached to the lower end of drill string it) for drilling in the normal way.

This application is a continuation-in-part of my copend- 7 described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise methods and forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. Apparatus for attachment to a rotary drill string for use in straightening a well bore comprising a drill bit, a centering guide having an outer diameter slightly less than the diameter of said bore, a lower flexible joint connected between said bit and one end of said centering guide, an upper flexible joint connected between the other end of said centering guide and the end of said rotary drill string, and a second centering guide between said lower ficxible joint and said bit for resisting lateral deviation of said bit during drilling.

2. A device for use in conjunction with a rotary drill string to straighten well bores comprising a drill bit having a cutting face, a lower drill collar attached to said bit, a lower centering guide positioned around said lower collar to provide a pivoting support in a bore hole at a predetermined distance from said bit, a link, a lower flexible joint connecting one end of said link and said lower collar, an upper centering guide carried on said link to form a pivot supporting said link for relative tilting in a deviated bore hole, and an upper flexible joint adapted to connect the other end of said link to the lower end of said drill string.

3. In a device for straightening a well bore having a deviated portion, the combination of a rotary drill string, an upper flexible joint connected to the lower end of said drill string, a link connected at one end to said upper joint, an upper centering guide carried on said link and of substantially larger diameter than said link to provide a pivot means for said link in said deviated bore, a lower flexible joint connected to the other end of said link, a lower drill collar connected to said lower joint, a drill bit fixed at the bottom of said lower collar, a lower centering guide carried on said lower collar and of such diameter with respect to said bit as to form pivot means for said lower collar in said bore at a predetermined distance from said bit, adjustable spring means urging each of said joints into axial alignment and providing for deviation of said joints against said spring means in response to application of a horizontal force to said upper flexible joint upon entry of said upper joint into said deviated bore portion, and means on each of said joints limiting their deviation from axial alignment.

4. In a device for straightening a well bore having a deviated portion, the combination of a rotary drill string, an upper flexible joint connected to the lower end of said drill string, a link connected at one end to said upper joint, an upper centering guide carried on said link in freely rotative relation thereto and of substantially larger diameter than said link to provide a pivot means for said link in said deviated bore, a lower flexible joint connected to the other end of said link, a lower drill collar directly connected to said lower joint, said lower collar having a bit at'its other end, a lower centering guide carried on said lower collar in freely rotative relation thereto and of such diameter with respect to said bit as to form pivot means for said lower collar in said bore at a predetermined distance from said bit, adjustable spring means urging both said flexible joints into axial alignment and providing for deviation of said joints against said spring means upon entry of said upper centering guide into said deviated bore portion and application of a horizontal force to said upper joint.

5. Apparatus for use in conjunction with a rotary drill string to straighten well bores comprising a rigid link member of substantially less outer diameter than the bore, a drill bit, a lower drill collar attached to said bit, a lower flexible joint connecting one end of said link member and said lower drill collar, an upper flexible joint adapted to connect the other end of said link member to the lower end of the drill string, a centering guide of slightly less outer diameter than the bore mounted on said link member intermediate its ends to provide a fulcrum for said link member which is maintained against substantial transverse movement in the bore, and means restraining said centering guide against axial movement along said link member to define the fulcrum point about which said link member may pivot at predetermined distances from opposite ends of said link member.

References Cited in the file of this patent UNITED STATES PATENTS 1,971,480 Earley Aug. 28, 1934 

